Removing tetrahydrofuran insolubles from a hydrogenation feedstock



Dec. 1,1970

INVENTORS LESTER u.

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L. M. RAPP ETAL RBIOVING' TBTRAHYDROFURAN INSOLUBLES FROM mm a. a, 1968 KHYDROGENATION, PEEDSTOCK United States Patent Office 3,544,449 Patented Dec. 1, 1970 3,544,449 REMOVING TETRAHYDROFURAN INSOLUBLES FROM A HYDROGENATION FEEDSTOCK Lester M. Rapp, Baton Rouge, La., and Adrian S. Wilk,

North Brunswick, N.J., assignors to Cities Service Research and Development Company, New York, N.Y., a corporation of Delaware Filed Dec. 3, 1968, Ser. No. 780,705 Int. Cl. Cg 23/10, 21/06 US. Cl. 20887 8 Claims ABSTRACT OF THE DISCLOSURE A method for hydrogenating heavy hydrocarbon oils containing material insoluble in tetrahydrofuran (THF) is disclosed. THF insolubles are precipitated and removed by contact with THF so that the remainder of the feed can be hdyrogenated in a conventional manner. By removing THF insolubles from the feed, the operability of the hydrogenation process may be significantly improved, especially for feed material containing large quantities of material insoluble in THF. THF insolubles are removed from either fresh feed or recycle feed or both so that the amount of THF insolubles in the total feed to the hydrogenation reaction zone is preferably less than 1 weight percent.

This invention relates to the hydrogenation of heavy hydrocarbon oil at least a portion of which boils above 975 F. and which contains substantial quantities of material insoluble in tetrahydrofuran (usually known as THF). Hydrogenation of such oils may be directed primarily to the cracking of heavy oil to form lower boiling material or may be directed primarily to desulfurization of the oil or a combination of these reactions. Other reactions commonly found in association with these reactions may of course also take place. The techniques for conducting hydrogenation of such feed stocks in a wide variety of operating conditions are well known and established in the art. Among the known techniques for hydrogenation of heavy hydrocarbon oils are those in which the hydrocarbon oil is passed, together with hydrogen-containing gas, in an intimate vapor-liquid mixture upwardly through a reaction zone containing a mass of particulate hydrogenation catalyst at a rate suificient to maintain the solids in random motion and under conditions such that there is a net chemical consumption of hydrogen and that the hydrocarbons in the diluent from the reaction zone are at least partially in the liquid phase. A suitable catalyst system for use in processes of this type is, for instance, the ebullated bed system described in more detail in US. Patent to Johanson Re. 25,770.

In the hydrogenation of heavy hydrocarbon oils, considerable difliculty has sometimes been encountered due to plugging and deactivation of catalyst by components of the feed and polymeric material believed to be formed by such components. It has been suggested previously to subject the feed to conventional propanedeasphalting to remove the heavier portions thereof. The portions of the feed which create problems in hydrogenation of such feed stocks are believed to be included in the heavier portions thus removed so that the deasphalted material can then be more readily processed in conventional hydrogenation units. It has been suggested in carrying out this type of process that the heavier materials removed in the propane deasphalting might later be blended back into the product from the hydrogenation treatment. Unfortunately, the quantities of feed removed by propane deasphalting or even by the use of somewhat heavier hydrocarbon solvents are such that blending all of the material back into the product makes it impossible in many cases to produce products of sufficiently low sulfur level and furthermore if the heavier portions are blended back, some of the metals or other components of such heavier portions may cause problems in further processing of the oil.

It has now been found that the components of certain heavy hydrocarbon feed oils which appear to be responsible for problems in hydrogenating such oils are concentrated in the portion of such feed stocks which are insoluble in tetrahydrofuran (THF). This material, which is also known as tetramethyleneoxide, is a known chemical solvent but is not normally used in the refining of hydrocarbon oils. Even the most troublesome heavy hydrocarbon feed stocks from the standpoint of operability in hydrogenation processes of the sort described above contain only relatively minor portions of material insoluble in THF. This material is believed to be for the most part material having relatively high molecular weight, e.g. above 500,000, and is of no real benefit in any of the conventional end uses of products of the hydrogenation of heavy hydrocarbon oils. The finding that removal of THF insolubles from heavy hydrocarbon oil feed stock can substantially improve the operability of such feed stocks in hydrogenation processes allows improvements in operability to be obtained without the disadvantage of removal of large portions of the feed stock as would be the case for instance with propane deasphalting.

According to the present invention, heavy hydrocarbon feed oil containing substantial quantities of material insoluble in THF is contacted with THF to precipitate the THF insoluble material therefrom. THF insoluble material is separated and the feed oil is then hydrogenated in a conventional manner.

The accompanying drawing is a somewhat diagrammatical illustration of a suitable arrangement of apparatus for carrying out a preferred embodiment of the present invention.

In conventional propane deasphalting, the heavy oil fraction being deasphalted is separated with the use of propane into an asphalt fraction and a deasphalted gas oil.

The separation is generally in the range of about 40 to 50 weight percent (wt. percent) asphalt and about 60 to 40 wt. percent deasphalted gas oil. By contrast, the THF insolubles in the heavy hydrocarbon feed oils rarely, if ever, exceed about 5 weight percent (wt. percent), so that by removing the THF insolubles the material removed from the feed oil need very seldom exceed about 5 wt. percent of the original feed oil.

It has been found that hydrogenation of heavy hydrocarbon fed oils containing more than 1.0 wt. percent material insoluble in THF is subject to operating difiiculties and it is therefore preferred when operating in accordance with the invention to treat feed stock containing more than 1 wt. percent THF insolubles with THF to reduce the total content of the THF insolubles in the feed stock to less than 1 wt. percent. In a preferred embodiment of the invention, the heavy hydrocarbon feed oil contains at least about 1.5 wt. percent THF insoluble material and the treated feed oil contains no more than about 0.5 wt. percent THF insoluble material.

Heavy hydrocarbon feed oils having significant portions, usually at least about 10 volume percent, boiling above 975 F. and which contain substantial amounts of material insoluble in THF, usually greater than 1 wt. mrcent and frequently greater than 1.5 wt. percent, are suitable feed oils for practicing the present invention. Particularly troublesome oils are those containing between about 1.5 and about 5 wt. percent THF insoluble material. Feed stocks of this type are usually residual oils, includ ing in some casesthose which occur naturally as in tar sands, and other so-called bottom of the barrel materials.

Vacuum or atmospheric residual oils are, for instance,

' desirable to treat all or a portion of the fresh feed for removal of THF insoluble material or it may be desirable to treat all or part of the residual recycle stream with THF in addition to or as an alternative to treatment of the fresh feed. In any event, it is generally desirable that the quantity of THF insoluble materialin the total feed to the hydrogenation reaction zone from both fresh feed and recycle streams should not exceed 1 wt. percent of such total feed.

While the present invention is beneficial in a wide variety of hydrogeneration processing operations, it is especially useful where heavy hydrocarbon feed oil of the type described above is treated for conversion of at least about 40 volume percent of material boiling above 975 F. to material boiling below 975 F. It is in these relatively high conversion operations that the greatest difi'iculties have previously been experienced with certain feed oils which have now been found to contain relatively high amounts of THF insoluble material.

Precipitation and removal of THF insoluble material from heavy hydrocarbon feed oil in accordance with the invention may be carried out in any suitable manner using any of the well known techniques for liquid contact operations. For instance, conventional countercurrent extraction equipment may be used or the THF may. merely be mixed with the feed to be treated, with the solids being removed as'a slurry from a settling drum. Apparatus suitable for conventional deasphalting operations may, for instance, be used for this purpose.

Since the THF insoluble material removed according to the present invention is harmful to the hydrogenation process and is not considered useful in other refining processes, it is generally preferred to recover such material for disposal, such as by burning as fuel. Because of the relatively high price of THF, it is preferred thatthe THF be recovered from the THF insoluble material prior to disposal of. the insolubles. This may be done by dissolving the THF insolubles in some suitable solvent such as orthodichlorobenzene or maybe accomplished by other means, such as by filtering the slurry of insolubles recovered from the THF treatment step with the liquid being returned to the hydrocarbon feed stream and the solids being disposed of. If desired, solids recov-= ered from the filtration may be slurried with suitable material such as cycle oil for convenience of transportation. The THF insoluble material may be disposed as waste or may conveniently be burned as fuel.

Due to the relatively high cost of the THF as mentioned above, it is preferred that the solution of THF and hydrocarbon feed oil recovered from the THF ex traction step be treated for recovery of THF before the feed oil is subjected to hydrogenation processing. This may conveniently be accomplished by means of a conventional stripping operation in which the THF is recovered from the oil and recycled to the extraction step. Liquid material recovered when THF insolubles are filtered as described above, may of course be similarly treated to separate THF from hydrocarbon feed oil. In this manner, it is generally possible to operate with comparatively small makeup requirements for TI-IF solvent. Typically, requirements for fresh solvent may be kept below about 1 wt. percent based on hydrocarbon feed oil being treated for removal of THF insoluble materials.

In treating hydrocarbon oils for removal of THF insolubles, suitable amounts of THF, such as between about 1 and about 20 times as much THF as feed oil being treated may be used in the extraction step. It will, of course, be understood that the amount of THF used and amount of fresh THF makeup needed willvary depending upon the amounts of THF insoluble material in the feed oil being treated, operating conditions, etc.

The THF extraction and hydrogenation processing steps may be carried out under suitable operating conditions. For instance, the THF treatment maybe conducted at atmospheric pressure while temperatures are maintained between about and about F. If desired, higher temperatures and pressures may be used so long as the THF remains in the liquid phase in the extraction step. The hydrogenation processing of the treated feed oil may be carried out under conventional elevated conditions of temperature and pressure. Temperatures normally range between about 700 and about 900 F. and pressures between about 1,000 andabout 3,000 p.s.i.g. partial pressure of hydrogen. Hydrogen rates between about 1,000 and about 10,000 standard cubic feet of hydrogen per barrel of feed (s.c.f./b.) are normal for such operations as are space velocities between about 0.2 and about 3.0 volumes of feed per hour per volume of reactor capacity (v./hr./v.).

Catalyst suitable for use in hydrogenating at least partially treated hydrocarbon feed oil in accordance with the present invention may be any suitable hydrogenation catalyst either natural or synthetic, the composition particle size and quantity of such catalyst forming no part of the present invention. Suitable catalysts include for example, cobalt, iron, molybdenum, nickel, tungsten and cobalt-molybdate, as well as their oxides and sulfides used alone or together with other suitable catalysts, such as naturally occurring silicates on suitable bases, such as alumina or silica alumina. While the catalyst may be employed in a suitable form, such as a fixed bed, slurry or the ebullated bed described in the above mentioned Iohanson patent, it is preferred that the catalyst be present in the reaction zone in the form of a mass of particulate solids, usually having a concentration of at least about 20 pounds per cubic foot of reaction zone, which mass is kept in random motion by upward flow of gas and liquid therethrough. Catalyst in such beds may be in the form of finely divided particles as small as about 40 microns or larger particles such as those described for use in the ebullated bed by the above-mentioned Johanson patent. The term hydrogenation catalyst as employed herein refers to any such catalyst irrespective of additional functions, such as cracking of the hydrocarbons which the catalyst may perform.

EXAMPLE 1 Referring to the drawing, fresh heavy hydrocarbon feed oil enters the process through a conduit 11 and passes through a valve 12 to an extraction unit 13. The feed introduced through the conduit 11 is Midcontinent low sulfur residuum material introduced at the rate of 147,000 lbs. per hour and has the following characteristics.

Gravity-10.5 API.

Sulfur-1.36 wt. percent.

Rams'botton Carbon-15.4 wt. percent. Viscosity SFS 210 F.699.

Pentane Insoluble Material-46.8 wt. percent. BS&W-Trace.

Ash0.04 wt. percent.

Nitrogen-0.39 wt. percent. Vanadium-60 p.p.m.

Nickel31 p.p.m.

IBP to 975 F.7.2 vol. percent.

Boiling above 975 .F.-92.8 vol. percent. THF Insoluble Material3.7 wt. percent.

In extraction unit 13, the feed introduced through the conduit 11 is contacted with THF solvent introduced into the extraction unit through a conduit 14. THF solvent is used in the ratio of approximately parts of solvent per part of feed. The extraction operation is carried out at a ttmperature of 150 F. and atmospheric pressure. From the extraction unit, a slurry of feed oil, THF and precipitated THF insoluble material is removed through a conduit 16 and passed to a filtration unit17 where solid THF insoluble material is separated and removed through a conduit 18. This material may be burned for fuel, with or without the addition of a slurrying liquid, or may be disposed or in any other suitable manner.

Liquid withdrawn from the extraction unit 13 with the THF insoluble material is conveniently recycled from the filtration unit 17 through a conduit 19 to a conduit 21 where it joins the mixture of purified feed oil and THF recovered from the extraction unit 13 and passes to a stripper 22. In the stripper 22, THF solvent is separated from the feed oil and recycled to the extraction unit 13 through the conduit 14. Fresh THF makeup solvent may be introduced through a conduit 23 as needed.

Feed oil containing reduced amounts of THF insoluble material passes from the stripper 22 through a conduit 24 and feed heater 25 to a hydrogenation reactor 26. A bypass conduit 27 and valve 28 are provided for bypassing the extraction unit and passing all or a portion of the fresh feed directly to the hydrogenation reactor if desired.

THF insoluble solids are removed as filter cake from the filtration unit 17 at the rate of 4704 lbs. per hour, thus reducing the amount of THF insolubles in the feed oil passed to the reactor 26 to 0.5 wt. percent. Feed oil passed through the conduit 24 to the hydrogenation reactor totals 142,296 lbs. per hour of THF soluble feed.

Hydrogen-containing gas is introduced into the hydrogenation reactor 26 through a conduit 29. In the reactor 26, a bed of particulate hydrogenation catalyst is maintained in an ebullated condition as taught by the abovementioned Johanson patent by the upward flow of liquid and gas through the catalyst bed. The catalyst in this example is an extrudate of cobalt-molybdenum on alumina and an average diameter of ,4, inch. The hydrogenation zone is maintained at a hydrogen partial pressure of 2250 p.s.i.g., a total pressure of 3000 p.s.i.g., a liquid space velocity of 0.7 v./hr./v., a temperature of 840 F. and a hydrogen rate at the reactor inlet of 4100 s.c.f./b. Catalyst addition rate is 0.10 pounds of catalyst per barrel of feed.

From the reactor 26, product is withdrawn through a conduit 30 and passed through a pressure reduction valve 31 to a separation zone 32 in which liquid is separated from vapor. Vapor from the separation zone 32 contains a high proportion of hydrogen and is recycled to the reactor through the conduit 29. Makeup hydrogen is added as needed through a conduit 33.

From the separation zone 32, liquid is withdrawn through a conduit 34 and passed to a fractionation unit 35 where it is fractionated to obtain a naphtha fraction withdrawn through a conduit 36, a fuel oil fraction withdrawn through a conduit 37 and a residual fraction withdrawn through a conduit 38. The residual fraction withdrawn through the conduit 38 is passed through a conduit 43 and valve 44 and recovered as a product of the process. Alternatively, all or a portion of the residual fraction from the conduit 38 may be passed through a conduit 39 and valve 41 to provide additional feed oil to the hydrogenation reactor 26 or may continue through the conduit 38 and a valve 42 to the conduit 11 from which it may be passed through the extraction unit 13 for removal of THF insolubles therefrom before being returned to the reactor 26. Recycle of residual material through the conduit 38 may be at a rate up to about 10 times the rate of introduction of fresh feed through the conduit 11.

As indicated in the above description, THF insoluble material may be removed either from the fresh feed or from a recycled residual fraction or both. If desired, a portion of either the fresh feed or recycle streams may be treated for THF insolubles removal by appropriate adjustment of the valves 12, 28, 41 and 42 to adjust the amounts of fresh feed and recycle material passing through the extraction unit 13. These proportions will, of course, vary depending upon the quantities of THF insoluble materials present in the fresh feed and recycle streams and the degree to which removal of such material is to be efiected. Generally speaking, the greater the degree of conversion desired in the hydrogenation reactor, the lower the maximum tolerable level of THF insoluble material in the feed to the reactor. It is therefore apparent that for certain operations, it may be desirable from an economic standpoint to allow small quantities of THF insoluble material, usually less than 1 wt. percent, to remain in the feed rather than attempting to remove all of such material. If the quantity of THF insoluble material in the fresh feed is sufiiciently low and the recycle rate of residual material sufliciently high, it may be possible to reduce the amount of THF insoluble material in the total reactor feed to the desired degree merely by removal of THF insolubles from the residual recycle stream as described above. Treatment of the recycle stream in this manner has a further advantage in that any THF insoluble material formed in the hydrogenation reactor will be removed, which of course is not the case if only fresh feed is treated for removal of THF insolubles.

EXAMPLE 2 Under the conditions of Example 1, including removal of large amounts of THF insoluble material from the feed, the hydrogenation reactor 26 may be operated successfully to convert 62% of the feed boiling above 975 F. to material boiling below 975 F. For this Example 2, the process is operated in a man-ner identical to that described above except that no THF insoluble materials are removed from the feed. Under these conditions the hydrogenation reactor 26 becomes plugged with coke and polymeric material and the process is considered inoperable. Without removal of THF insoluble the reactor 26 is operable only to a maximum conversion level of 30% at a temperature of 820 F. and a space velocity of 1.0 v./hr./v.

While the invention has been described above with respect to preferred embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention and it is intended to cover all such changes and modifications in the appended claims.

We claim:

1. The process for the hydrogenation of heavy hydrocarbon feed oil at least 10 volume percent of which boils above 975 F. and which contains material insoluble in tetrahydrofuran which comprises:

(a) contacting at least a portion of such feed oil with tetrahydrofuran solvent to thereby selectively precipitate material insoluble in tetrahydrofuran and produce a feed oil fraction containing reduced amounts of material insoluble in tetrahydrofuran; and

(b) in a hydrogenation reaction zone contacting said feed fraction containing reduced amounts of material insoluble in tetrahydrofuran with hydrogenation catalyst and hydrogen-containing gas under hydrogenation conditions to thereby hydrogenate such fraction.

2. The process of claim 1 in which the heavy hydrocarbon feed oil originally contains more than 1 wt. percent material insoluble in tetrahydrofuran and the feed oil fraction containing reduced amounts of such material contains less than 0.5 wt. percent of such material.

3. The process of claim 2 in which the feed oil fraction containing reduced amounts of material insoluble in tetrahydrofuran is substantially free of such material.

4. The process for the hydrogenation of heavy hydrocarbon feed oil at least 10 volume percent of which boils above 975 F. and which contains more than 1 wt. percent material insoluble in tetrahydrofuran which comprises:

'(a) contacting at least a portion of such feed oil with tetrahydrofuran solvent to thereby selectively PIG! cipitate material insoluble in tetrahydrofuran; (b) separating material precipitated in step (a) to produce a feed oil fraction containing lessthan 1% material insoluble in tetrahydrofuran; and (c) in a hydrogenation reaction zone contacting said feed oil fraction containing less than 1 Wt. percent material insoluble in tetrahydorfuran with hydrogenationation catalyst and hydrogen-containing gas under hydrogenation conditions to thereby hydrogenate such fraction. 5. The process of claim 4 in which product from the reaction zone is fractionated and a high boiling fraction thereof containing at least 10 vol. percent oil boiling above 975 F. is treated with tetrahydrofuran solvent for removal of tetrahydrofuran insolubles therefrom and is then recycled for use as at least a portion of the heavy hydrocarbon feed oil to the hydrogenation reaction zone.

6. The process of claim 5 in which only the recycled portion of the feed oil to the hydrogenation reaction zone is treated with tetrahydrofuran solvent.

7. The process of claim 4 in which the heavy hydrocarbon feed oil contains at least about 1.5 wt. percent material insoluble in tetrahydrofuran and the hydrogenation reaction zone is operated so as to convert at least a 8 vol. percent of the feed oil material boiling below 975 F.-

8. The process of claim 7 in which the hydrocarbon feed oil fraction containing less than 1 wt. percent material insoluble in tetrahydrofuran is passed in an intimate vapor liquid mixture upwardly through a mass of particulate hydrogenation catalyst in the reaction zone at a sufficientrate to'maintain the catalystin random motion and under such operating conditions including a hydrogen partial pressure of between about 1,000 and about 3,000 p.s.i.g.,'a temperature of between about 700 and about 900 F. and a liquid hourly space velocity between about 0.3 and about 5.0 that there is a net chemical consumption of hydrogen and that the hydrocarbons in the efliuent from said reaction zone are, at least partially in liquid phase.

boiling above 975 F. to

References Cited UNITED STATES PATENTS 1,998,399 4/1935 Pevere 208325 2,966,450 12/ 1960 Kimberlin et a1 20887 3,132,088 5/ 1964 Beuther et al. 20886 3,306,840 2/ 1967 Myers et al 20887 HERBERT LEVINE, Primary Examiner US. Cl. X.R. 20886, 251, 325 

